Wind Tunnel Balances

Aerodynamic Test Equipment

Vehicle development steps and optimization of aerodynamic properties are often carried out in Wind Tunnel facilities. Even though many investigations can be done with numerical methods, still realistic tests with true air flow simulation around the vehicle are indispensable. The demand for new modern Wind Tunnels with the capability of air flow simulation especially at the underside of the vehicle combined with a high accuracy of force measurement is now even growing worldwide. The HORIBA Wind Tunnel Balance System together with its integrated moving ground system fulfils both requirements excellently.

The improvement of vehicle aerodynamics is an important step to optimize fuel consumption, driving comfort, performance and acoustic. A commonly, well known factor describing the quality of the aerodynamics is the drag coefficient Cd, which can be measured in a Wind Tunnel together with other aerodynamic coefficients using a Wind Tunnel Balance. The vehicle is placed upon the measuring platform of the balance. The Wind Tunnel Balance now allows the precise measurement of six forces and moments induced by the air flow. In a Wind Tunnel the air flow at the underside of the vehicle is not completely realistic, because the vehicle is not moving in the tunnel. In reality the vehicle is moving while the air is at rest. In the Wind Tunnel a boundary layer exists close to the test section floor. In modern Wind Tunnels thus special methods and equipment are used to improve air flow simulation at the underside of the vehicle. The Horiba Wind Tunnel Balance can be equipped with a moving ground system (also called ‘5-Belt-System’) which makes the air flow at the underside and around the wheels much more realistic. This moving ground system is build- up of a central moving belt unit (also called ‘Rolling Road System’) which is running at wind speed between the wheels and of four wheel spinning units which are rotating the wheels with wind speed. In this case the four wheel spinning units are also part of the force measuring system of the balance. Maximum speeds of up to 250 km/h are possible.

The HORIBA Wind Tunnel Balance is a platform-type balance. A computer program is used to calculate the forces Fx (Longitudinal-Force), Fy (Lateral-Force), Fz (Vertical-Force) and the three moments Mx (Roll-Moment), My (Pitch-Moment), Mz (Yaw-Moment) from the six force sensor signals.